My friend called me and asking for help because his computers were infected by Conficker worm which is a well known worm, even until now, even though it was first known at the end of last year. This worm has caused a lot of trouble, thus Microsoft is giving away US$25.000 just to find out who created this worm and put him/her behind the bar. Microsoft also put a resource for their customer to learn more about conficker
I asked him whether he updated his antivirus database regularly and he did. Next, i asked him whether his computers are connected to the Internet all the time and the answer is yes. OK, so every computers are connected to the Internet. My next question is about security patches. It seems that he trusted the antivirus application very well and didn't take any other precaution, for example patching the operating system itself. This is the main problem for him and for many other home users.
Anti virus is not a silver bullet to protect your computer against attack from outsider. You may have to regularly patch your operating system and applications to make intruders/attackers harder to penetrate and corrupt your system.
I hope he learn something from this event and prepare better system protection in the future
Me myself never get too interested in virus/worms ever since i used Linux regularly